Artmink has both Free and Premium versions. Free usage is limited to uploading one image per appraisal. With a Premium subscription, you can submit up to 4 (four) images per appraisal. A bonus of subscribing is Artmink.com membership, where you can do appraisals, view your iOS app aprpaisals, search-filter appraisals, save appraisals as PDF and scan QR codes, which are generated for each appraisal.
Link to End User License Agreement (Apple Standard Agreement)
https://www.apple.com/legal/internet-services/itunes/dev/stdeula/